In the context of an HLA-DPB1 mismatch between a recipient and a donor (Panel A), an rs9277534G-linked (high-expression) mismatch is hypothesized to be a visible target for donor-mediated graft-versus-host (GVH) recognition. Red HLA molecules represent the mismatched HLA-DPB1 in the recipient, blue molecules represent the donor’s mismatched HLA-DPB1, and green molecules are shared (matched) between the recipient and the donor. Black arrows pointing from the donor toward the recipient represent the GVH vector of allorecognition. The size of the upward-pointing gray arrows indicates the magnitude of the GVH response. In the context of an HLA-DPB1 match between a recipient and a donor (Panel B), peptides (minor histocompatibility antigens) presented by an rs9277534G-linked (high-expression) HLA-DPB1 molecule in a recipient may be a more visible target for donor-mediated GVH recognition. Diverse peptides presented by HLA are shown as purple and blue circles and red, blue, and green triangles.